CATV networks use an infrastructure of interconnected coaxial cables, signal splitters and combiners, repeating amplifiers, filters, trunk lines, cable taps, drop lines and other signal-conducting devices to supply and distribute high frequency “downstream” signals from a main signal distribution facility, known as a “headend,” to the premises (homes and offices) of subscribers to the CATV services. The downstream signals transfer multimedia content to subscriber equipment, such as television sets, telephone sets and computers. In addition, most CATV networks also transmit “upstream” signals from the subscriber equipment back to the headend of the CATV network. For example, the subscriber uses a set top box to select programs for display on the television set. As another example, two-way communication is essential when using a personal computer connected through the CATV infrastructure to the public Internet. As a further example, voice over Internet protocol (VoIP) telephone sets use the CATV infrastructure and the public Internet as the communication medium for transmitting two-way telephone conversations.
To permit simultaneous communication of upstream and downstream CATV signals and the interoperability of the subscriber equipment and the equipment associated with the CATV network infrastructure outside of subscriber premises, the downstream and upstream CATV signals are confined to two different frequency bands. The downstream frequency band is within the range of 54-1002 megahertz (MHz) and the upstream frequency band is within the range of 5-42 MHz, in most CATV networks. The entire CATV frequency band is therefore 5-1002 MHz.
The downstream signals are delivered from the CATV network infrastructure to the subscriber premises at a CATV entry adapter, which is also commonly referred to as an entry device, terminal adapter or a drop amplifier. The CATV entry adapter is usually a multi-port device which provides a multiplicity of ports or connectors for connecting coaxial cables. A separate coaxial cable is connected to each of the ports and extends within the subscriber premises to the location of the subscriber equipment. Some homes have coaxial cables extending to cable outlets in almost every room, because of the many different types of subscriber equipment used in different rooms. For example, television sets are commonplace throughout the home. The multiple ports of the CATV entry adapter deliver downstream CATV at each cable outlet and conduct upstream CATV signals back through the premises coaxial cables to the CATV entry adapter, which delivers the upstream CATV signals to the CATV network.
In addition to television sets, computers and telephones, a relatively large number of other entertainment and multimedia devices are available for use in homes. For example, a digital video recorder (DVR) is used to store broadcast programming, still photography and moving pictures in a memory medium so that the content can be replayed on a display or television set at a later time selected by the user. As another example, computer games are also played at displays or on television sets. Such computer games may be obtained or played over the Internet from the CATV network or from media played on play-back devices or game consoles connected to displays or television sets. As a further example, receivers which receive satellite-broadcast signals may be distributed for viewing or listening throughout the home. These types of devices, including the more-conventional television sets, telephone sets and devices connected to the Internet by the CATV network, are generically referred to as multimedia devices.
The desire to use multimedia devices at multiple different locations within the home or subscriber premises has led to the creation of the Multimedia over Coax Alliance (MoCA). MoCA has developed specifications for products to create an in-home entertainment network for interconnecting presently-known and future multimedia devices. The MoCA in-home network uses the subscriber premise or in-home coaxial cable infrastructure originally established for distribution of CATV signals within the subscriber premises, principally because that cable infrastructure already exists in most homes and is capable of carrying much more information than is carried in the CATV frequency band. A MoCA network is established by connecting MoCA interface devices at the cable outlets in the rooms of the subscriber premises. The MoCA network is used to transmit multimedia content from one MoCA interface device to another.
The MoCA interface devices implement a MoCA communication protocol which encapsulates the multimedia content normally sent and received by the multimedia devices within MoCA packets and then communicates these MoCA packets between selected ones of the other MoCA interfaces devices connected at other cable outlets. The receiving MoCA interface device removes the encapsulated multimedia content, and delivers it to the connected computer, digital television or set-top box or other multimedia device from which then presents that multimedia content.
Each MoCA interface device is capable of communicating with every other MoCA interface device in the MoCA network to deliver the multimedia content throughout the home or subscriber premises. The entertainment or multimedia content that is available from one multimedia device can be displayed, played or otherwise used at a different location within the home, without having to physically relocate the multimedia device from one location to another within the home. The in-home network communication of multimedia content is considered beneficial in more fully utilizing the multimedia devices present in modern homes. The MoCA interface devices also pass the upstream and downstream CATV signals between the CATV entry adapter and the subscriber devices.
Since the MoCA network may function simultaneously with the normal operation of the CATV services, the MoCA signals communicated between MoCA interface devices utilize a frequency range of 1125-1525 MHz, which is outside of the frequency band of CATV signals. This so-called D band of MoCA signals is divided into eight different frequency ranges, D1-D8, and these eight different D frequency ranges are used to assure communication between the selected MoCA interface devices. For example, the D-1 band at 1125-1175 MHz may be used to communicate CATV television programming content between a MoCA interface device connected to a set-top box in a main room of the house and another MoCA interface device connected to a television set in bedroom of the house, while a MoCA interface device connected to a computer gaming multimedia device in a basement room of the house simultaneously communicates computer game content over the D-6 band at 1375-1425 MHz to a computer located in a recreation room of the house. The MoCA frequency band also includes other frequency ranges outside of the CATV frequency band, but the D band is is used to establish connections and communicate content between the MoCA interface devices.
Using the in-home coaxial cable as the principal communication medium substantially simplifies the implementation of the MoCA network, but there are certain disadvantages in doing so. The D band MoCA frequencies have the capability of passing through the CATV entry adapter and entering the CATV network where they may then enter a nearby subscriber's premises. The presence of the MoCA signals at the nearby subscriber's premises compromises the privacy and security of the information originally intended to be confined within the original subscriber premises. The MoCA signals from the original subscriber premises which enter through the CATV network to the nearby subscriber premises also have the potential to adversely affect the performance of a MoCA network in nearby subscriber's premises. The conflict of the MoCA signals from the original and nearby subscriber premises may cause the MoCA interface devices to malfunction or not operate properly on a consistent basis.
Another undesirable aspect of using a MoCA for communication between the various multimedia devices is that a relatively large MoCA network with many cable outlet ports has the effect of deteriorating the strength of the downstream CATV signal. Because in-home multimedia devices frequently require access to the CATV network in order to send upstream CATV signals as well is to receive downstream CATV signals, the in-home coaxial cable infrastructure must commonly connect all of the CATV cables and CATV ports within the home to a common connection with the drop cable that supplies the CATV signal and services to the home. The common connection is usually achieved in the CATV entry adapter, which provides output ports that connect to the coaxial cables extending within the home to each separate location or room. A splitter within the CATV entry adapter divides the CATV downstream signals into two or more reduced-power copies of the input signal, and supplies each copy to a separate outlet port. Similarly, upstream signals from the subscriber equipment connected to each of the coaxial cables are combined in the splitter and then passed upstream through the CATV entry adapter into the CATV network.
The typical splitter is passive, which means that the power of the input signal is divided among the copies of the output signals split from the input signal. Each copy of the signal therefore has diminished power or strength, and the lower strength copies will not have the same quality as the input signal. In general terms, the quality is the strength of the signal relative to the strength of the inherent ambient noise. Since the inherent ambient noise generally cannot be diminished and is usually a constant, lowering the strength of the signal relative to the noise reduces the signal-to-noise ratio. The signal-to-noise ratio is a recognized measure of the quality of a signal. A lower signal-to-noise ratio represents a lesser quality signal.
Because many homes require a relatively large number of cable outlet ports, for example six or more, the downstream CATV signal must be split into a comparable relatively large number of copies. The greater number of signal splitters required to generate the requisite number of separate copies of the downstream CATV signal diminishes the strength of the downstream signal copies. The quality of CATV service available in an in-home network with a relatively large number of cable output ports therefore suffers, because the strength of the CATV signal available at each of these ports is substantially diminished due to the extent of signal splitting required.
On the other hand, Upstream CATV signals from the subscriber equipment do not occur as frequently as downstream CATV signals. Furthermore, upstream signals are generally of a higher power because they are generated immediately by the subscriber equipment within the home. Consequently, the reduction in CATV signal strength applies principally to downstream CATV signals, which of course provide the multimedia content to the subscriber. It is the quality of the multimedia content observed by the subscriber that forms the basis for the subscriber's opinion of quality of service.
To compensate for downstream CATV signal strength reduction caused by splitting, some entry adapters include amplifiers to increase the strength of the copies of the downstream CATV signals. Of course, including an amplifier along with the signal splitter makes the signal transmission dependent upon the presence of adequate electrical power to operate the amplifier. The power for the amplifier is derived from commercial sources within the household. If the commercial power supply is temporarily interrupted, or if the power supply equipment within the home ceases operating properly, the customer perceives a CATV problem and reports the problem to the CATV service provider. The CATV service provider must thereafter send a service or repair person to the home of the subscriber in order to identify and remedy the problem. Such service calls are a significant expense for a CATV service provider. CATV service providers therefore attempt to eliminate as many of the potential points of failure as possible in the equipment supplied by the CATV service provider, to reduce service calls and repair costs. Including an amplifier in a CATV entry adapter creates a potential point of failure, and for that reason most CATV service providers wish to avoid using CATV entry adapters with amplifiers. However, in those relatively large in-home networks with multiple outlets for connecting multiple multimedia devices, there has been little previous choice but to use amplifiers in conjunction with splitters in order to obtain the desired downstream CATV signal strength that represents a high quality of service.